London: Nothing reflects the evolution of football's modern full back more than Manchester City's decision to spend around 120 million pounds ($156.35 million) on buying three in 10 days — with a fourth possibly on the way.

Benjamin Mendy became the latest to arrive at the Etihad Stadium on Monday for a reported ‎£49 million, joining Danilo, signed from Real Madrid for ‎£26 million on Sunday, and Kyle Walker, a ‎£45 million buy from Tottenham Hotspur earlier this month.

In making these signings, City's manager Pep Guardiola has both reshaped his defence and provided an exciting new range of options out wide.

Pep Guardiola will be banking on the exuberance of youth, this season. Reuters

Where once the full back's job was to nullify the opposition winger, now he is a focal point of attack too, with Guardiola banking on this trio's ability to deliver chances for his equally expensive strikers.

For Monaco, French international Mendy completed five assists in Ligue 1 and three in the Champions League last season, figures that suggest more goals should now flow from Guardiola's problem left side.

Perhaps only City would pay such a fee — four times the amount Monaco paid Marseille for the 23-year-old just 12 months ago — but Mendy's pace, technique and intelligence were major factors in the French side's success last season.

Guardiola, who witnessed Mendy's worth close up in Monaco's Champions League knockout win over City last season, has persuaded his paymasters to fork out serious money for a player who could make his debut against Real Madrid in Los Angeles on Wednesday

"Benjamin has all the qualities we are looking for in a full back," City's director of football, Txiki Begiristain said on Monday. "For such a young player, he has a wealth of top-level experience.

"He is undoubtedly one of the world's best full backs, our number one target in this position."

City are almost certain to rotate their full backs, with Danilo, who can play on both sides, acting as a cover for Mendy and Walker. Guardiola is also reported to be in the market for another right back to complete a very expensive set.

Last season City's full back problems frustrated Guardiola, who cited his lack of options as the excuse for City's inability to break down neighbours United in April's goalless Manchester derby.

On that occasion Guardiola named 32-year-old Pablo Zabaleta and Aleksandar Kolarov, 31, with Bacary Sagna, 34, and Gael Clichy, 31, on the bench — a quartet with a combined age of 128.

"We don't have full backs to go up and down, up and down, because all of them are 33, 34 years old, so I adapt with the quality of players," said Guardiola, who became so exasperated that he even experimented with midfielder Fernandinho there.

All four of City's recognised full backs from last season have now departed with Guardiola's class of 2017-18 primed to form a dazzling wide link with Leroy Sane, Raheem Sterling and Bernardo Silva, another new signing from Monaco.

With Sergio Aguero, Gabriel Jesus, Kevin De Bruyne and David Silva in the middle, City threaten goals all over the pitch, assuming Guardiola can knit his talents together.

If he can't, City may have just made the most expensive mistake in football history.